package Huawei;

import java.util.Scanner;

public class HJ34图片整理 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int a[] = new int[128];
            String str = in.next();
            for (int i = 0; i < str.length(); i++) {
                int k = str.charAt(i);//统计出现次数
                a[k]++;
            }
            for (int j = 48; j < a.length; j++) {//从'0'开始输出
                if (a[j] != 0)
                    for (int b = 0; b < a[j]; b++)
                        System.out.print((char) j);
            }
            System.out.println();
        }
    }
}
